AC to DC conversion using single supply opamp

[atferrari]

The OP mentions up to 350 mA. Can anyone describe what componentes that curren flows through? At lost here.

 

[audioguru]

The OP mentions up to 350 mA. Can anyone describe what componentes that curren flows through? At lost here.

The input is 350mA RMS and is loaded with a 10 ohms resistor. The resistor is used as a "burden" which is the resistor used in a current meter and the circuit in this thread detects and measures the voltage across this resistor then calculates the current.

 

[MikeMl]

The TS has some stringent requirements. Here is a hack using a 4pole Butterworth 10Hz LPF following a half-wave rectifier. Note I adjusted the burden resistor to prevent V(in) clipping.

Note the settling times of V(out). Note the residual ripple, which could be reduced by using a full-wave rectifier. Conversely, using FW, you might get by with a 2-pole LPF.

 

[MikeMl]

Here is why you cannot do this with a single pole filter with such a short rise-time, even starting with full-wave rectification. Note the residual ripple at V(lp)

You can play around with various more agressive active Low-Pass opamp filters here.

 

[Mikebits]

Every single Multisim schematic posted on all electronics forums shows the lines wandering all over the place and there are chicken pox dots all over it.

That is because they are most likely using screenshots as opposed to printing out a schematic. And they have sloppy technique when making the schematic.

 

[audioguru]

The link to the Analog Devices filter wizard does not work.
Why not use a modern multi-order switched capacitor Butterworth lowpass filter instead of capacitors, resistors and opamps. It makes an excellent filter.

 

[MikeMl]

The link to the Analog Devices filter wizard does not work.

Try this instead. Click on Filter Wiz

Why not use a modern multi-order switched capacitor Butterworth lowpass filter instead of capacitors, resistors and opamps. It makes an excellent filter.

Why don't you post one?

 

[audioguru]

Years ago I used switched capacitor filters made by National Semi but they are not made anymore. Here is a Maxim one:

 

[alec_t]

Unfortunately that Maxim filter IC needs a 4.5V-5.5V supply. The TS has a 3.3V supply.

 

[MikeMl]

So here is my final attempt. The Input I(Rb) is a 50Hz sinusoidal current burst (15 pulses) that starts at 100ms and ends at 400ms. The simultion is repeated with the amplitude of I1 stepping from +-50mA to+-350mA in steps of 50mA.

The current is converted to a voltage by the burden resistor Rb. U1 and U2 are a full-wave rectifier that creates the full-wave rectified signal at V(fw). The average value this signal is proportional to the input current, but has its first ripple component at 100Hz.

We need a filter U3 U4 that smooths V(fw) to get rid of the 100Hz ripple, but settles within 100ms. It takes a 4th Order Bessel LPF to do that.
You need Rail-to-Rail IN/OUT 1MHz 3.3V opamps to pull this off.

I would like to see you repeat this simulation in Multisim, including the filter rise-fall response. I think that LTSpice is far superior to Multisim in setting up a complex analysis like this. Note how easy it is to start-stop the sinusoidal current, and to repeat the sim at multiple amplitudes. For the students of LTSpice, I am including the .asc file so you can run this sim.

 

[ericgibbs]

hi may,
If the use of a MCU/PIC controller is allowed, this option has a sinusoidal peak detector and a MCU interrupt pulse generator, which occurs at the peak voltage.
The MCU could be programmed to read/save the ADC, On Interrupt, the peak value, if the peak exceeds to set level for more than 200mSec, a MCU output alarm pin is set High.

The test Sine wave input is set for 1v thru 5v
E

 

[mayuriv]

470μF will take all day to charge. Use a much lower value like this:

I am not getting a smooth dc after doing this...Can you suggest resistor value?

 

[MikeMl]

I am not getting a smooth dc after doing this...Can you suggest resistor value?

As I showed in post #24!

 

[crutschow]

I am not getting a smooth dc after doing this...Can you suggest resistor value?

You need to use the circuit Mike showed in post #30.
Anything less will not meet your criteria for both rise-time and smooth dc.
If you want to muck around with different circuits, have at it, but don't bother us if they don't work.

 

[MikeMl]

...
If you want to muck around with different circuits, have at it, but don't bother us if they don't work.

Couldn't have said it better, myself.

I'm tired of casting pearls before swine...

 

[mayuriv]

So here is my final attempt. The Input I(Rb) is a 50Hz sinusoidal current burst (15 pulses) that starts at 100ms and ends at 400ms. The simultion is repeated with the amplitude of I1 stepping from +-50mA to+-350mA in steps of 50mA.

The current is converted to a voltage by the burden resistor Rb. U1 and U2 are a full-wave rectifier that creates the full-wave rectified signal at V(fw). The average value this signal is proportional to the input current, but has its first ripple component at 100Hz.

We need a filter U3 U4 that smooths V(fw) to get rid of the 100Hz ripple, but settles within 100ms. It takes a 4th Order Bessel LPF to do that.
You need Rail-to-Rail IN/OUT 1MHz 3.3V opamps to pull this off.

I would like to see you repeat this simulation in Multisim, including the filter rise-fall response. I think that LTSpice is far superior to Multisim in setting up a complex analysis like this. Note how easy it is to start-stop the sinusoidal current, and to repeat the sim at multiple amplitudes. For the students of LTSpice, I am including the .asc file so you can run this sim.

View attachment 104764

Thanks a lot Sir...This circuit is perfect.It has fulfilled my requirement
Sorry for the late reply..I was not at work..

Can you explain the circuit in detail?

 

[MikeMl]

...
Can you explain the circuit in detail?

I thought I already did...

 

[mayuriv]

I thought I already did...

which opamp have you used?
I need an opamp with less quiescent current...